1. Field of the Invention
This invention relates to ionizers, which are designed to remove or minimize static charge accumulation. Ionizers remove static charge by generating air ions and delivering those air ions to a charged target.
One type of ionizer uses corona electrodes to produce air ions. During operation, debris can build up on the corona electrodes and change the ionizer performance. Performance parameters include balance, swing, and discharge time.
Sensor feedback to the ionizer is desirable for two reasons. The first reason is maintaining the ionizer's balance, swing, and discharge time within predetermined limits. The second reason is notifying the user when balance and discharge time breach the predetermined limits.
In a conventional closed loop feedback system, one sensor is connected to one ionizer. The one-to-one correspondence is a simple case, and feedback signals can be generated within the sensor itself.
The current invention uses novel feedback architecture and signal processing to allow individual or multiple sensors to control individual or multiple ionizers. An intermediate module receives raw signals from one or more sensors, and creates the best feedback instruction. In turn, the best feedback signal is forwarded to one or more ionizers.
The position of each sensor is considered when the intermediate module creates the best feedback signal.
2. Description Of Related Art
Ionizers remove static charge by ionizing air molecules, and delivering those generated air ions to a charged target. The air ions are most commonly created by high voltage applied to corona electrodes. Positive air ions neutralize negative static charges, and negative air ions neutralize positive static charges.
From a performance view, ionizers are defined by balance, discharge time, and swing.
Balance is a measure of closeness to zero volts. After the initial charge is removed from a target, that target would ideally equilibrate at zero volts from ground. In practice, the target equilibrates near zero volts from ground, but seldom exactly at zero volts.
Balance is normally specified as a range around zero. For example, ionizer balance may be specified as −5 volts to +5 volts. If voltages between −5 and +5 volts do not affect products handled within the workstation, the products can be handled safely. But if voltages between −2 and +2 volts affect products handled within the workstation, an ionizer with a tighter balance specification is appropriate.
Discharge time is a measure of how fast a given level of charge can be removed from a charged target. Low discharge times are better than high discharge times. For example, an ionizer with a discharge time of 3 seconds could be applied to a moving charged target that only remains under the ionizer for 3 seconds.
Swing is the peak-to-peak voltage that an AC or pulsed DC ionizer produces at the target. Static sensitive products can be damaged by high swing, even though the average balance is near zero.
Historically, ionizer feedback has consisted of one sensor connected directly to one ionizer. Although this is useful, positional errors are inherent. The single sensor does not represent the ionizer's performance everywhere within the work zone. Balance may be positive in one location, and negative in a second location. Discharge time and swing also vary with location.
A single sensor also reflects grounded objects in the vicinity. For example, a grounded metal object close to a sensor could skew the sensor's measurements. If the metal object preferentially absorbs positive air ions, the sensor will report a negative balance. In addition, the negative discharge time will increase.
Swing is reduced when the metal object reduces the density of both positive and negative air ions.
Prior art sensors that are connected directly to an ionizer also miss the opportunity to filter out irregular perturbations. The reason is that the prior art sensors are based on average analog responses, and the perturbation is lost in the averaging. Consider a grounded robot arm that travels between the ionizer and the sensor. When the robot arm is directly under the ionizer, the number of air ions that reach the sensor is reduced. Simultaneously, the balance of air ions may shift.
With an intermediate digital module, the opportunity would exist to correct for positional biases, correct for positional variances, and correct for temporal disturbances. Although no prior art systems have pursued this architecture, there is a need.